Falls and their consequences are among the major problems in the medical care of older individuals. The long-term goal of this research is to establish the efficacy of a scientifically grounded and mechanism-based therapeutic intervention for improving balance function and preventing falls in older people. When human balance is challenged, protective stepping is a vital strategy for preventing a fall during activities of daily life. Many older people at risk for falls have particular difficulties with successfully stepping sideways as a protective response to loss of balance in the lateral direction. We propose that age-related declines in lateral balance function through impaired protective stepping that precipitates falls, result from neuromechanical (NM) limitations in hip abductor-adductor (AB-AD) muscle strength (torque and power). Moreover, we hypothesize that these functional and NM impairments are reversible with combined, high intensity induced, step training and muscle strengthening. The specific aims are to conduct a double blind, randomized, and controlled trial with four training arms that will compare the effects of 12 weeks of training and assess its durability after 3 months of no training in community living older adults at risk for falls by determining: 1) the effect of (a) waist-pull induced step training, (b) hip AB-AD muscle strengthening, and (c) a combined step training and muscle strengthening program compared to (d) a standard flexibility and relaxation program involving minimal-intensity exercises (control) on the protective stepping response to an external balance perturbation, as measured by i) the number of multiple balance recovery steps, and ii) first step length;and 2) the effect of high intensity step training, with and without the strengthening intervention, compared to the control group on a) maximum hip AB- AD joint torque and power. A secondary aim will assess whether protective stepping performance and hip AB- AD muscle strength discriminate between a) fallers and non-fallers identified by retrospective fall history at the time of study enrollment, and b) the prospective fall frequency of the different intervention groups during 1-year follow-up post-training. PUBLIC HEALTH RELEVANCE: The relevance of this research to public health lies in its focus on understanding the causes of age-associated falls and on the development of effective interventions for minimizing the devastating economic, societal, and personal consequences of falls among older people.